FIG. 3.

Immunogenicity and protective efficacy of recombinant EtpA tested in a murine model of ETEC colonization. Mice immunized intranasally with either IVX908 alone (controls) or IVX908 plus recombinant, nonglycosylated polyhistidine-tagged EtpA (30 μg/dose) on days 0, 22, and 42. On day 63 the mice were given 8.5 × 10⁴ CFU of WT ETEC (H10407) by oral gavage, and the degree of colonization was assessed approximately 24 h after inoculation. (A) Anti-EtpA (total IgG, IgM, and IgA) responses (ELISA) in serum obtained on day 63 prior to challenge. Control sera have been diluted 1:50; IVX908/rEtpA sera were diluted 1:1,028. (P < 0.0001 [two-tailed Mann-Whitney]). (B) Titers of anti-EtpA antibody in mice vaccinated with either IVX908 or IVX908/rEtpA. Horizontal lines represents geometric mean titers (GMT). (C) ELISA data for salivary antibody from mice (at a saliva dilution of 1:2) immunized with either IVX908 or IVX908/rEtpA (P < 0.0001 [two-tailed Mann-Whitney]). (D) ETEC H10407 recovered from the small intestine after challenge of mice vaccinated with either IVX908 or IVX908/rEtpA (P = 0.01 [one-tailed Mann-Whitney]). Dashed horizontal bars represent geometric mean values throughout. Bacteria were recovered from the small intestine as previously described (1).